The "active takeoff crack" refers to a critical type of crack that can occur in aircraft, particularly in the landing gear and adjacent structures. This phenomenon is a major concern for aircraft operators, maintainers, and regulatory bodies, as it can lead to catastrophic failures during takeoff, compromising the safety of passengers, crew, and the aircraft itself.

An active takeoff crack is a dynamic crack that propagates rapidly during the takeoff phase of flight, typically during the high-load conditions encountered during rotation and initial climb. This type of crack often occurs in the heat-treated steel or high-strength aluminum alloys used in landing gear components, such as the gear beam, fork, or axle.